The present invention relates generally to a shaft sealing module for sealing a shaft which extends, driving rotationally, from a normal pressure chamber into a high vacuum chamber. As an example, manufacturing processes in the semi-conductor field largely take place under vacuum, in particular coating processes. During these processes the substrates to be coated must be moved. As the drive elements for these are usually mounted on the atmospheric or normal pressure side of these machines or devices, the substrates can only be moved if rotational movements are transmitted into the evacuated system via a sealed shaft.
These processes often take place at very high vacuum pressures, often of the order of 10−8 mbar. In order, however, to be able to work with small vacuum pumps and avoid the penetration of gases (O2, N2, CO2) harmful to these processes into the high vacuum chamber from the normal pressure chamber via the shaft arrangement, very high requirements are imposed on the shaft seal.
In such shaft seals it is known to use a “magnetic fluid” comprising a suspension of ferritic nanoparticles in an oil with high vapor pressure which is maintained in a gap about the rotating shaft via a particular arrangement of magnets and pole shoes. However, many coating processes involve the use of high frequency electric field. In such instances, the use of “magnetic fluids” is not possible because the magnets of the shaft seals makes it difficult or impossible to control the high frequency currents flowing on the surfaces. Additionally, the magnetic fluid shaft seals can be damaged by the flowing currents and hence become ineffective.